Composition and process for enhanced oil recovery

ABSTRACT

The present invention includes a cost effective custom-designed blend of organic chemicals to stimulate oil production. The invention includes a chemical composition for use in drilling operations for oil recovery and the method of using the chemical composition. The chemical composition includes an ammonia compound, an alcohol, and aqueous carrier solution. The aqueous carrier solution is of sufficient volume such that it is operable to fully dissolve the ammonia compound and alcohol in the aqueous carrier solution.

RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication Ser. No. 60/561,669 filed on Apr. 13, 2004, which isincorporated by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a chemical composition and the use ofthe chemical composition to increase oil production and reserves.

BACKGROUND OF THE INVENTION

When oil is present in subterranean rock formations such as sandstone,carbonate, or shale, the oil can generally be exploited by drilling aborehole into the oil-bearing formation and allowing existing pressuregradients to force the oil up the borehole. This process is known asprimary recovery. If and when the pressure gradients are insufficient toproduce oil at the desired rate, it is customary to carry out animproved recovery method to recover additional oil. This process isknown as secondary recovery. Primary oil recovery followed by secondaryoil recovery, such as injection of water or gas to force out additionaloil, are able to remove generally around 30 percent of the total oilcontent of an oil reservoir in many fields.

In waterflooding, pressurized water is injected into the oil-bearingformation after primary recovery and produced from neighboringhydrocarbon production wells. First hydrocarbon, and subsequentlyhydrocarbon and water are recovered from the production well.

Even after secondary recovery such as waterflooding, large amounts ofthe original oil remain in place. The fraction of unrecoverablehydrocarbon is typically highest for heavy oils, tar, and complexformations. In large oil fields, more than a billion barrels of oil canbe left after conventional waterflooding. In addition to waterflooding,carbon-dioxide-miscible flood projects are also used. Tertiary recoverythen becomes the focus. It is estimated that current tertiary oilrecovery techniques have the ability to remove an additional 5 to 20percent of the oil remaining in the reservoir. Given the current worlddependence on fossil hydrocarbons, the development of effective tertiaryoil recovery strategies for higher oil recovery promises to have asignificant economic impact. Current methods of tertiary recover areeffective, but expensive. Current tertiary methods still leavesignificant amounts of original oil in place in the field.

Much of the remaining oil in place after primary and secondary recoveryis in micro-traps due to capillary forces or adsorbed onto mineralsurfaces through irreducible oil saturation as well as bypassed oilwithin the rock formation. Encouraging movement of normally immobileresidual oil or other hydrocarbon is commonly termed tertiary recovery.It is known to use microorganisms such as bacteria to dislodge the oilin micro-traps or adsorbed onto mineral surfaces to recover additionaloil during the waterflooding phase. This typically involves theintroduction of a microorganism from outside. These microbes createmethane, which is then recovered.

It is also know that polymers and gelled or crosslinked water-solublepolymers are useful in enhanced oil recovery and other oil fieldoperations. They have been used to alter the permeability of undergroundformations in order to enhance the effectiveness of water floodingoperations. Generally, polymers or polymers along with a gelling agentsuch as an appropriate crosslinking agent in a liquid are injected intothe formation. Both microbe-based and polymer-based enhanced recoveryare expensive processes.

The diagenetic fabrics and porosity types found in varioushydrocarbon-bearing rocks can indicate reservoir flow capacity, storagecapacity and potential for water or CO₂ flooding. The goal is to forceoil out of high-storage-capacity but low-recovery units into a higherrecovery unit. This allows an increase of recovery of oil over predictedprimary depletion recovery such that a higher percentage of the originaloil in place is recovered.

Traditional tertiary recovery operations include injection of the CO2 orwater into the well. There is a need for an improved composition forenhanced oil recovery. It would be advantageous to use commerciallyavailable traditional injection facilities to reduce capitalexpenditures.

To fully capitalize on their national resources, oil-producing countriesmust enhance domestic petroleum production through the use ofadvanced-oil recovery technology. Operating companies, typicallyconservative in stating recoverable reserves, have a need to increaserecoverable reserves from proven reserves as opposed to development ofunproven reserves. There is a need for cost effective oil recoverytechniques to maximize removal of original oil in place per field. Thereis a need for a cost effective oil recovery technique to reducedevelopment costs by more closely delineating minimum field size andother parameters necessary to successfully recover oil. There is a needfor tertiary recovery that can utilize simple or current applicationprocedures.

U.S. Pat. No. 6,225,263 teaches a method of increasing the recovery ofoil and/or gas from an underground formation by injecting into theformation an aqueous solution of a mono alkyl ether of polyethyleneglycol.

U.S. Pat. No. 3,902,557 describes a method of treating the formationsurrounding a well by injection of a solvent including a C₄ to C₁₀ alkylether of a polyglycol ether containing a C₄ to C₁₀ alkyl ether of apolyglycol ether containing 10-22 carbon atoms per molecule. C₄ to C₈monoalkyl ethers of tri and tetra ethylene glycols are preferred inparticular the hexyl ether while the butyl ether is also mentioned. Thesolvent may be diluted with an organic liquid such as alcohol, e.g.isopropanol.

FR Patent No 2735524 is directed toward a method of secondary andtertiary recovery through the use of alcohol in an amount of 1 to 5% byweight to solvate asphaltenes.

A need exists for a cost effective composition and method of use of thecomposition to improve enhanced oil recovery. There is a need tocapitalize on the original oil in place that is unrecovered by primaryand/or secondary recovery method.

SUMMARY OF THE INVENTION

In order to meet one or more of these needs, the present inventionadvantageously provides a composition and method for tertiary oilrecovery. The invention includes a cost effective custom-designed blendof organic chemicals to stimulate oil production. Whether throughsurfactant or solvent action, this composition mobilizes residual oiltrapped in the reservoir.

The invention includes a chemical composition for use in drillingoperations for oil recovery and the method of using the chemicalcomposition. The chemical composition includes an ammonia compound, analcohol, and aqueous carrier solution. The aqueous carrier solution isof sufficient volume such that it is operable to fully dissolve theammonia compound and alcohol in the aqueous carrier solution. Whileheating is not required, slight elevation of the temperature has shownpositive effects. The chemical composition exhibits the ammonia compoundand the alcohol substantially distributed throughout the carrier fluid.

In a preferred embodiment, the alcohol useful in the chemicalcomposition of the invention contains from about one to about six carbonatoms. The alcohol is preferably non-aromatic. More particularly,alcohols containing one to four carbons are particularly useful, i.e.methyl, ethyl, propyl, and/or buytl alcohol. Of the propyl alcohols,isopropyl alcohol is particularly preferred. Alcohol is preferred in anamount of approximately 4 to 16 percent by volume of the chemicalcomposition.

In the chemical composition of the invention, a preferred carriersolution is water. This solution can also be salt water such as producedwaters. Aqueous carrier solutions are preferred. In a preferredembodiment, there is only one carrier solution and it is just water. Thecarrier solution in an amount of approximately 76 to 94 percent byvolume of the chemical composition is preferred.

The ammonia compound of the chemical composition is preferably ammoniaor ammonium hydroxide. The ammonia compound present in an amount ofapproximately 2 to 8 percent by volume of the chemical composition.

The preferred amounts of the ammonia compound and the alcohol define arange of ratios that are preferred. The preferred ratio of alcohol toammonia compound is between approximately 1:1 alcohol to ammonia andapproximately 3:1 alcohol to ammonia, the ratio being on a volume basis.The ratio of approximately 2:1 alcohol to ammonia is particularlypreferred.

This invention also includes a process for recovering hydrocarbons froma hydrocarbon formation containing hydrocarbon reserves. The process ofthe invention includes introducing the chemical composition into thehydrocarbon formation in an amount effective to substantially increasethe recovery of hydrocarbons from the formation. The subsequent recoveryof hydrocarbons from the hydrocarbon formation can be through the samewell or through other wells in the field.

The current invention can be used as secondary and/or tertiary recovery.The composition of the invention is believed to improve the permeabilityof the formation adjacent to the well bore.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features, advantages and objects of theinvention, as well as others that will become apparent, may beunderstood in more detail, more particular description of the inventionbriefly summarized above may be had by reference to the embodimentthereof that are illustrated in the appended drawings, which form a partof this specification. It is to be noted, however, that the drawingsillustrate only a preferred embodiment of the invention and aretherefore not to be considered limiting of the invention's scope as itmay admit to other equally effective embodiments.

FIG. 1 is a simplified flow diagram of injection of the chemicalcompound of the invention into a reservoir; and

FIG. 2 is a simplified flow diagram of equipment useful for oneembodiment of the invention that includes injecting produced water withthe chemical composition of the invention into a well

DETAILED DESCRIPTION

For simplification of the drawings, figure numbers are the same in FIG.1 and FIG. 2 for various streams and equipment when the functions arethe same, with respect to the streams or equipment, in each of thefigures. Like numbers refer to like elements throughout, and prime,double prime, and triple prime notation, where used, generally indicatesimilar elements in alternative embodiments.

Alcohols can generally be defined as R—OH where R is a combination ofcarbon and hydrogen atoms, water being excluded from such definition.The preferred alcohol of the invention is straight chained, as opposedto an aromatic, with a continuous chain of carbon atoms from 1 to 8carbons long. Saturated alcohols are generally preferred as they tend tobe more stable than unsaturated alcohols. Methyl alcohol, ethyl alcohol,i-propyl alcohol, n-propyl alcohol and butyl alcohol are preferred.Propyl alcohol is particularly preferred. Of the propyl alcohols,isopropyl alcohol is particularly preferred. Mixtures of methyl, ethyl,propyl and/or butyl alcohols to create the alcohol of the invention arealso encompassed in this invention. A mixture of ethyl and propylalcohol is preferred. As the chemistry of the alcohol molecule isdominated by the functional OH group, it is understood by those skilledin the art that other alcohols can be effective alone or in combination.However, the use of only one alcohol having a continuous chain of 1 to 8carbons or only one alcohol, that alcohol being the mixture of the oneto eight carbon alcohols without other alcohols, is effective andpreferred.

Notably, alcohols can also be created in situ, for example, through thereaction of salts with appropriate reagents in the presence of water.Creation of the alcohol in situ is also encompassed in this invention.

Additionally, surfactants can be added to the chemical composition inorder to decrease the water-oil interfacial tension and to improve theefficiency, but the invention provides efficient and cost-effectiveresults through the use of a mixture of only the ammonia compound, thealcohol and the carrier solution.

Ammonia is added to the chemical composition. Ammonia can be provided inmany forms, the preferred forms being anhydrous ammonia and ammoniumhydroxide. Ammonia can be produced by reaction or dissociation. Ammoniumions such as dissolved ammonium salts are also encompassed within theinvention. Ammonia is quite soluble in water, dissolving to the extentof about 700 volumes in 1 volume of solvent. The dissolving process isaccompanied by the reaction NH3+H2O thereby producing NH4++OH—. This isreferred to as ammonium hydroxide. Therefore, ammonium hydroxide, whichis often produced commercially with significant amounts of ammonia inwater, is included in the term ammonia in this invention. Alsoencompassed are other precursors that form the ammonium ion in situ.

Isopropyl alcohol, also known as isopropanol, has a formula of C₃H₈O andis unsaturated. This is a particularly preferred alcohol of theinvention. It is noted that isopropyl alcohol has a boiling point of82.4 degrees C. and specific gravity: 0.78 at 20 degrees C. The air odorthreshold concentration of isopropyl alcohol to be as 22 parts permillion (ppm) parts of air. Contact between isopropyl alcohol and airoccasionally results in the formation of peroxides, another possibleelement of the composition, whether added or created in situ. Therefore,an alternate embodiment of the invention includes the addition ofperoxide to the ammonia compound and alcohol. Isopropyl alcohol isbelieved to change the wettability of the strata, particularly at theinterface of the fracture and rock matrix. Viscocification is achievedby altering the properties of the reservoir fluid.

EXAMPLE 1

Anhydrous ammonia is used in this example, Baume 26. isopropyl anhydrousalcohol ammonia water volume % 8 4 88

The resulting composition was diluted five times such that there was 1part composition of the invention and 4 parts diluent. Water was used asthe diluent. Salt water from produced waters can also be used. This wastested on well and substantially increased recovery was observed.

EXAMPLE 2

Test is identified as test #1300. Following is a chart comparing thechemical composition of the invention to connate water: SurfaceViscosity Density #1300 mPa · s g/cm3 pH Chemical 0.79 0.958 11.635Connate 0.83 0.985 9.439 water #1 Connate 0.78 0.982 9.362 water #2

This example was run at concentration of 0% (to mimic connate water),0.2%, 0.5%, 1.0%, 2.0%, 4.0%, 6.0%, 8.0%, 10%, 15%, 20% and 100%.

The results of these tests indicate that the solubility of the chemicalcomposition is good in different concentration.

EXAMPLE 3

Test is identified as test #700. Following is a chart comparing thechemical composition of the invention to connate water: SurfaceViscosity Density #700 mPa · s g/cm3 pH Chemical 0.83 0.964 11.791Connate 0.83 0.985 9.439 water #1 Connate 0.78 0.982 9.362 water #2

The chemical can be recovered and recycled to further decrease costs.The chemical composition does not appear to react with oil nor is asignificant amount trapped in the formation. Therefore, the chemicalcomposition can be separated from oil/fluid and recycled.

While the invention has been shown or described in only some of itsforms, it should be apparent to those skilled in the art that it is notso limited, but is susceptible to various changes without departing fromthe scope of the invention.

For example, while this invention has been described as useful fortertiary recovery, it can be used to stimulate production at any pointduring the life of the well, including in conjunction with secondaryflooding. While traditional injection equipment has been described, theinvention includes any method of bringing the chemical composition intocontact with the oil producing strata. Various means of forming thechemical composition, including creation in situ, are encompassed inthis invention. Uses for the chemical composition related to theproperties recognized in the composition are also encompassed withinthis invention. The method of the invention may be applied to wellstimulation treatments such as water blocking, sand consolidation,sandstone acidizing and methods of increasing the recovery of oil suchas tertiary oil recovery. The chemical composition can be injected intoa producing well or at a distance from a producing well to drive thehydrocarbons to the well. Gelled or viscosified means of delivering thischemical composition are also encompassed in the invention.

1. A chemical composition for use in drilling operations for oilrecovery, the chemical composition comprising: an ammonia compound, analcohol; and an aqueous carrier solution, the aqueous carrier solutionbeing of sufficient volume operable to fully dissolve the ammoniacompound and alcohol in the aqueous carrier solution, the ammoniacompound and the alcohol being substantially distributed throughout thecarrier fluid.
 2. The chemical composition of claim 1 wherein thealcohol contains from about one to about six carbon atoms and isnon-aromatic.
 3. The chemical composition of claim 2 wherein the alcoholis propyl alcohol.
 4. The chemical composition of claim 3 wherein thealcohol is isopropyl alcohol.
 5. The chemical composition of claim 2wherein the alcohol is butyl alcohol.
 6. The chemical composition ofclaim 2 wherein the alcohol is ethyl alcohol.
 7. The chemicalcomposition of claim 2 wherein the alcohol is methyl alcohol.
 8. Thechemical composition of claim 1 wherein the carrier solution is water.9. The chemical composition of claim 1 wherein the carrier solutionconsists essentially of water.
 10. The chemical composition of claim 1wherein the ammonia compound is ammonia.
 11. The chemical composition ofclaim 1 wherein the ammonia compound is ammonium hydroxide.
 12. Thechemical composition of claim 1 wherein the alcohol is in an amount ofapproximately 4 to 16 percent by volume of the chemical composition. 13.The chemical composition of claim 1 wherein the ammonia compound is inan amount of approximately 2 to 8 percent by volume of the chemicalcomposition.
 14. The chemical composition of claim 1 wherein the carriersolution is in an amount of approximately 76 to 94 percent by volume ofthe chemical composition.
 15. The chemical composition of claim 1wherein the alcohol and the ammonia compound define a ratio of alcoholto ammonia compound, the ratio being between approximately 1:1 alcoholto ammonia and approximately 3:1 alcohol to ammonia, the ratio being ona volume basis.
 16. A process for recovering hydrocarbons from ahydrocarbon formation containing hydrocarbon reserves, the processcomprising the steps of: introducing the chemical composition of claim 1into the hydrocarbon formation in an amount effective to, when added tothe formation, substantially increase the recovery of hydrocarbons fromthe reserve; and recovering hydrocarbons from the hydrocarbon formation.17. The process for recovering hydrocarbons of claim 16 furthercomprising the step of recovering a significant amount of the chemicalcomposition subsequent to the introduction of the chemical compositioninto the hydrocarbon formation such that the chemical composition can beused again in the hydrocarbon formation.